Interlayer insulating film, interconnection structure, and methods of manufacturing the same

ABSTRACT

This invention provides an interlayer insulating film for a semiconductor device, which has low permittivity, is free from the evolution of gas such as CFx and SiF 4  and is stable, and a wiring structure comprising the same. In an interlayer insulating film comprising an insulating film provided on a substrate layer, the interlayer insulating film has an effective permittivity of not more than 3. The wiring structure comprises an interlayer insulating film, a contact hole provided in the interlayer insulating film, and a metal filled into the contact hole. The insulating film comprises a fluorocarbon film provided on the substrate layer, and a surface of the fluorocarbon film is nitrided.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional of application Ser. No. 11/922,476filed Dec. 19, 2007, now pending, which is the National Stage ofApplication No. PCT/JP2006/312292, filed on Jun. 20, 2006, which isbased upon and claims the benefit of priority from Japanese PatentApplication No. 2005-179591, filed Jun. 20, 2005, the entire contents ofwhich are incorporated herein by reference. This application claims onlysubject matter disclosed in the parent application and thereforepresents no new matter.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates to a multilayer interconnection structure,particularly an interlayer insulating film structure, of a board, suchas a semiconductor-element or semiconductor-chip mounting board or awiring board and further relates to a semiconductor device having themultilayer interconnection structure, a wiring board having themultilayer interconnection structure, and an electronic device includingthem. Moreover, this invention relates to a method of manufacturing themultilayer interconnection structure and methods of manufacturing thesemiconductor device having the multilayer interconnection structure,the wiring board having the multilayer interconnection structure, andthe electronic device including them.

2. Background Art

Conventionally, an interlayer insulating film is formed for insulationbetween interconnection layers in a multilayer interconnection structureon a semiconductor substrate or the like.

In such a multilayer interconnection structure, a problem of signaldelay due to the parasitic capacitance between interconnections and theinterconnection resistance has become unignorable and it has beenrequired to use an interlayer insulating film having a low permittivity(Low-k).

As such an interlayer insulating film, attention has been paid to thefact that a fluorocarbon film (hereinafter referred to as a CFx film)has a very low permittivity and thus can reduce the parasiticcapacitance between interconnections. However, the CFx film is very weakagainst water and poor in adhesion. Therefore, the CF film is formed onan underlayer such as an SiCN layer, an Si₃N₄ layer, or an SiO₂ layer,but there has been a problem in the bottom and top surfaces of the CFfilm (i.e. the beginning and end of the film formation).

Conventionally, a CFx film is formed by the use of a plasma processingapparatus using a fluorocarbon gas (referred to as a CFx gas, e.g. aC₅F₈ gas), for example, as described in Patent Document 1.

As described in Patent Document 2, this CFx gas is originally used foretching and thus there has been a problem that if the plasma treatmenttemperature is high, an underlayer is etched to produce a siliconfluoride (SiF₄) gas.

Further, there has been a problem that water and gases such as CFx andSiF₄ are released from the surface of the formed CF film to form acontamination source.

Patent Document 3 describes that a formed CFx film is annealed in an N₂atmosphere at 400° C. to 450° C., so that outgassing after the filmformation is small in amount.

Further, plasma treatment is performed using a single rare gas whenforming an oxide film, a nitride film, an oxynitride film, or the likeas an underlying metal on a silicon semiconductor. In the case of usinga single rare gas, use is made of a krypton (Kr) gas or a xenon (Xe) gashaving a large sectional area for collision with electrons and a lowplasma electron temperature for the purpose of reducing plasma damage topost-treatment (e.g. see Patent Document 4).

-   Patent Document 1: Japanese Unexamined Patent Application    Publication (JP-A) No. 2002-220668-   Patent Document 2: Japanese Unexamined Patent Application    Publication (JP-A) No. 2002-16050-   Patent Document 3: Japanese Unexamined Patent Application    Publication (JP-A) No. H11-162962-   Patent Document 4: Japanese Unexamined Patent Application    Publication (JP-A) No. 2002-261091

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide an interlayerinsulating film of a semiconductor device or the like, which has a lowpermittivity, is free from generation of gases such as CFx and SiF₄, andis stable.

It is another object of this invention to provide a method ofmanufacturing an interlayer insulating film of a semiconductor device orthe like, which has a low permittivity, is free from generation of gasessuch as CFx and SiF₄, and is stable.

It is still another object of this invention to provide aninterconnection structure of a semiconductor device or the like,comprising an interlayer insulating film having a low permittivity andbeing free from generation of gases such as CFx and SiF₄ and stable.

It is a further object of this invention to provide a method ofmanufacturing an interconnection structure of a semiconductor device orthe like, comprising an interlayer insulating film having a lowpermittivity and being free from generation of gases such as CFx andSiF₄ and stable.

It is still another object of this invention to provide methods ofmanufacturing the above interlayer insulating film and the aboveinterconnection structure.

Means for Solving the Problem

According to one aspect of the present invention, there is provided aninterlayer insulating film which includes an insulating film formed onan underlayer, said interlayer insulating film having an effectivepermittivity of 3 or less.

In the aspect of the present invention, it is preferable that theinsulating film includes a first fluorocarbon film formed on theunderlayer and a second fluorocarbon film formed on the firstfluorocarbon film and having a permittivity lower than that of the firstfluorocarbon film.

In the interlayer insulating film, it is also preferable that the firstfluorocarbon film has a thickness of 5 to 10 nm and the secondfluorocarbon film has a thickness of 280 to 500 nm. Furthermore, it ispreferable that each of the first and the second fluorocarbon films hasa low permittivity. Specially, it is preferable that the permittivity ofthe second fluorocarbon film is 1.5 to 2.5. Moreover, it is preferablethat the underlayer includes at least one of an SiCN layer, a siliconnitride (Si₃N₄) layer, an SiCO layer, and an SiO₂ layer formed on a basebody. Specially, it is preferable that the first fluorocarbon film isprovided for preventing generation of a fluorosilane gas produced by areaction with the underlayer.

In addition, the first fluorocarbon film may be formed by CVD using aplasma generated by using a Xe or Kr gas. On the other hand, the secondfluorocarbon film may be formed by CVD using a plasma generated by usingan Ar gas.

It is also preferable that a surface of the second fluorocarbon film isnitrided and a thickness of a nitrided portion of the surface is 1 to 5nm, preferably 2 to 3 nm.

It is preferable that a film formed on the insulating film and made ofat least one of Si₃N₄, SiCN, SiCO is provided.

According to another aspect of the present invention, there is provideda method of forming a fluorocarbon film on an underlayer using afluorocarbon gas and two or more kinds of rare gas. The method includesa first step of forming a first fluorocarbon film on the underlayer by aplasma generated by using a rare gas other than an Ar gas and a secondstep of forming a second fluorocarbon film on the first fluorocarbonfilm by a plasma generated by using an Ar gas.

In the method according to the aspect of the present invention, it ispreferable that the first fluorocarbon film is formed up to a thicknessof 5 to 10 nm and the second fluorocarbon film is formed up to athickness of 280 to 500 nm on the first fluorocarbon film. Specially, itis preferable that the second fluorocarbon film has a permittivity lowerthan that of the first fluorocarbon film.

In addition, It is preferable that the underlayer is a layer includingat least one of an SiCN layer, an Si₃N₄ layer, an SiO₂ layer, and anSiCO layer formed on a base body and that the rare gas used in the firststep is a Xe gas.

Furthermore, the film of at least one kind of Si₃N₄, SiCN, and SiCO maybe formed by adding at least one of a nitrogen gas and an oxidizing gasto the rare gas and flowing a SiH₄ gas as a reactive gas.

According to still another aspect of the present invention, there isprovided a method of manufacturing a multilayer interconnectionstructure of a semiconductor device or the like. The method includes astep of forming a fluorocarbon film as at least portion of an interlayerinsulating film, a step of annealing the fluorocarbon film, and a stepof nitriding a surface of the fluorocarbon film.

In the present invention, it is preferable that the annealing step isperformed in an inert gas without exposure to the atmosphere. It is alsopreferable that the nitriding step is performed in a plasma using an Argas and using an N₂ gas or in a plasma using an N₂ gas. In the lattercase, it is preferable that the nitriding step is performed at atemperature of 200° C. or higher, more preferably at a temperature of300° C. to 400° C.

Furthermore, it is preferable that the method further includes, beforeor after the annealing step, a step of irradiating the surface of thefluorocarbon film with a rare gas plasma.

According to yet another aspect of the present invention, there isprovided an interconnection structure which includes an interlayerinsulating film having an insulating film formed on an underlayer, acontact hole formed in the interlayer insulating film, and a metalfilled in the contact hole, the interlayer insulating film having aneffective permittivity of 3 or less.

In the aspect of the present invention, it is preferable that the metalfilled in the contact hole contains copper and a barrier layer includingat least a layer of a fluoride of nickel is interposed between theinterlayer insulating film and copper. The fluoride of nickel is, forexample, nickel difluoride, but is not limited thereto. This fluoride ofnickel is formed by MOCVD or is formed by forming a film of nickel byPVD (Physical Vapor Deposition) and then fluorinating the film. Theinterlayer insulating film is preferably a fluorocarbon film.

It is preferable that the insulating film includes a first fluorocarbonfilm formed on the underlayer and a second fluorocarbon film formed onthe first fluorocarbon film and having a permittivity lower than that ofthe first fluorocarbon film, and that the first fluorocarbon film has athickness of 5 to 10 nm while the second fluorocarbon film has athickness of 280 to 500 nm. Specially, it is preferable that thepermittivity of the second fluorocarbon film is 1.5 to 2.5. Furthermore,it is preferable that the underlayer includes at least one of an SiCNlayer, an Si₃N₄ layer, and an SiO₂ layer formed on a base body. Herein,the first fluorocarbon film is provided for preventing generation of asilicon fluoride gas produced by a reaction with the underlayer.

Furthermore, it is preferable that the interconnection structure furtherincludes a film formed on the fluorocarbon film and containing at leastone of Si₃N₄, SiCN, and SiCO, and that a nitrided film is provided at asurface portion of the second fluorocarbon film.

According to a further aspect of the present invention, there isprovided a method of manufacturing an interconnection structure. Themethod includes a first step of forming a first fluorocarbon film on anunderlayer using a fluorocarbon gas and a rare gas whose plasma has anelectron temperature lower than that of Ar, and a second step of forminga second fluorocarbon film on the first fluorocarbon film by a plasmagenerated by using an Ar gas.

Herein, it is preferable that the first fluorocarbon film is formed in athickness of 5 to 10 nm while the second fluorocarbon film is formed ina thickness of 280 to 500 nm. Furthermore, it is also preferable thateach of the first and the second fluorocarbon films has a lowpermittivity. Specially, it is preferable that the permittivity of thesecond fluorocarbon film is adjusted to 1.5 to 2.5.

Furthermore, it is preferable that the underlayer includes at least oneof an SiCN layer, an Si₃N₄ layer, an SiCO layer, and an SiO₂ layerformed on a base body. It is also preferable that the rare gas used inthe first step is a Xe gas.

Moreover, a film of at least one of Si₃N₄ or SiCN, and SiCO may beformed by adding at least one of a nitriding gas and an oxidizing gas tothe rare gas, and flowing an SiH₄ gas as a reactive gas. It ispreferable that a surface of the second fluorocarbon film is nitrided.

In the aspect of the present invention, it is preferable that the methodincludes, in addition to the first and the second steps, a step offorming a contact hole in the fluorocarbon films and a step of filling ametal in the contact hole. It is also preferable that the method furtherincludes a step of forming a barrier layer for preventing diffusion ofthe metal filled in the contact hole.

According to a yet further aspect of the present invention, there isprovided a method of cleaning a chamber, comprising, after generating aplasma in a pressure-reduced chamber to form a fluorocarbon film on asubstrate placed in the chamber, generating a plasma using a mixed gasof hydrogen and oxygen in the chamber, thereby cleaning an inner wall ofthe chamber.

Effect of the Invention

According to this invention, it is possible to provide an interlayerinsulating film of a semiconductor device, which has a low permittivity,is free from generation of gases such as CFx and SiF₄, and is stable,and a method of manufacturing it.

Further, according to this invention, it is possible to provide aninterconnection structure comprising such an interlayer insulating filmand a method of manufacturing it.

Further, according to this invention, by first forming a fluorocarbonfilm by plasma CVD using a Xe or Kr gas, it is possible to reduceoutgassing of SiF-based gases and further to prevent stripping of thefluorocarbon film. Then, by forming a main portion of the fluorocarbonfilm by CVD in an Ar gas plasma, it is possible to reduce the effectivepermittivity of the fluorocarbon film.

Further, according to this invention, by nitriding the surface of thefluorocarbon film, there is an effect of largely reducing outgassing andthere is also an effect of preventing stripping of an insulating filmformed on the fluorocarbon film.

Further, according to this invention, by providing a barrier layer ofnickel difluoride on the inner surface of a via hole or a contact hole,it is possible to prevent Cu in the hole from diffusing into the barrierlayer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a conventional interlayer insulating filmstructure of a semiconductor device according to prior art.

FIG. 2 is a diagram showing an interconnection structure according to anembodiment of this invention.

FIG. 3 is a schematic sectional view showing the structure of aninterlayer insulating film used in the interconnection structure of FIG.2.

FIG. 4 is a schematic sectional view showing a plasma processingapparatus according to an embodiment of this invention.

FIG. 5 is a diagram showing the relationship between the distancebetween a shower plate and an electrode, and the electron density (ev)for an Ar plasma, a Kr plasma, and a Xe plasma.

FIG. 6 is a diagram showing a schematic structure of an outgas measuringtest apparatus.

FIG. 7 represents diagrams showing the underlayer dependence of SiFxoutgassing, wherein (a) shows a CFx film formed on a Si underlayer(CFx/Si), (b) shows a CFx film formed on an SiO₂ underlayer (CFx/SiO₂),and (c) shows a CFx film formed on an Si₃N₄ underlayer (CFx/Si₃N₄).

FIG. 8 is a diagram showing the temperature dependence of SiF-based gasamounts.

FIG. 9 is a diagram showing time-dependent changes of SiF₄ spectra.

FIG. 10 represents diagrams showing the temperature dependence ofSiF-based outgas amounts, wherein (a) shows the temperature dependenceof outgas amounts in the case of film formation using Ar and (b) showsit in the case of film formation using Xe.

FIG. 11 is a diagram showing the temperature dependence of SiFx gasamounts when an underlayer is made of Si.

FIG. 12 represents diagrams showing the temperature dependence ofSiFx-based outgas amounts, wherein (a) shows the outgas amounts from aCFx film obtained by treatment with C₅F₈/Xe at 26.6 Pa (200 m Torr) for5 seconds, then treatment with C₅F₈/Ar at 26.6 Pa (200 mTorr) and, afterannealing, treatment with Ar at 26.6 Pa (200 m Torr) for 5 seconds and(b) shows the outgas amounts from a CFx film obtained by treatment (5seconds) in which a Xe plasma is on and C₅F₈ is introduced, then, afterthe introduction of C₅F₈ is off and the Xe plasma is off, Ar/C₅F₈treatment for 3 minutes and then Ar+N₂ treatment for 5 seconds.

FIG. 13 shows the temperature dependence of SiFx outgas amounts when anunderlayer is made of Si.

FIG. 14 is a diagram showing the TDS outgas spectra of a CFx film of 120nm formed on a Si underlayer.

FIG. 15 is a diagram showing the temperature dependence of CFx outgasamount, after annealing, of a CF film formed on an SiO₂ underlayer.

FIG. 16 is a diagram showing the temperature dependence of releasedwater amount, after CF-film annealing, of a CF film formed on an SiO₂underlayer in the same manner.

FIG. 17 is a diagram showing the fluorocarbon outgas characteristicsafter Ar/N₂ plasma treatment using the apparatus of FIG. 5 and theresults of thermal desorption spectrometry (TDS) measurement.

FIG. 18 represents diagrams showing the temperature dependence ofCFx-based outgas amount in the case where C₅F₈ is introduced inAr-plasma treatment, then the introduction is stopped in the plasmatreatment, and then the Ar-plasma treatment is stopped, wherein (a)shows the relationship between the relative intensity of CFx outgas andthe time and (b) shows the relationship between the H₂O concentration(ppb/cm²) for released water and the time.

FIG. 19 represents diagrams showing the annealing temperature dependenceof outgas amounts of a CFx film, wherein (a) shows the outgas amount ofa CF-based gas and (b) shows the outgas amount of an H₂O gas.

FIG. 20 represents diagrams showing the spectral of various outgasesaccording to a difference in leaving time of a CFx film, wherein (a)shows the results of measurement after being left standing in theatmosphere for 12 hours after annealing at 400° C. and (b) shows theresults of measurement after being left standing in the atmosphere for48 hours without annealing.

FIG. 21 represents diagrams showing the temperature dependence ofSi-based outgas amount, wherein (a) shows the temperature dependence ofCFx outgassing and (b) shows the temperature dependence of waterrelease.

FIG. 22 represents diagrams showing the surface nitriding effects,wherein (a) and (b) show the CFx outgassing effect and the water releaseeffect, respectively, when an Ar/N₂ plasma was irradiated for 5 secondsafter annealing.

FIG. 23 shows the results of measurement of a sample formed with a CFxfilm and subjected to Ar/N₂ plasma irradiation after annealing like inFIG. 17, using an X-ray photoelectron spectrometer (ESCA: ElectronSpectroscopy for Chemical Analysis).

FIG. 24 represents diagrams showing the film forming conditiondependence of outgas amounts of a CFx film, wherein (a) shows CF-basedoutgassing and (b) shows H₂O-based outgassing.

FIG. 25 represents diagrams showing the results of outgassing in thecase of Ar/N₂ plasma treatment after annealing a CFx film formed to 400nm, wherein (a) shows the results with no nitriding being the normalcondition and (b) shows the results with nitriding. It is seen thatoutgassing is small in amount by the Ar/N₂ nitriding treatment.

FIG. 26 is a diagram showing the outgas TDS spectra of an SiCN filmin-situ formed on a CFx film (SiCN/CFx) formed on a Si underlayer.

FIG. 27 is a diagram showing the temperature dependence of CF-basedoutgas amount when a CFx film formed at 200° C. is annealed at 350° C.

FIG. 28 is a diagram showing the temperature dependence of outgas amountin the case where a film is formed at 200° C. and then annealed at 350°C. and, further, the surface thereof is nitrided by an Ar/N₂ plasma at200° C.

FIG. 29 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 350° C. and no annealing is carriedout.

FIG. 30 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 350° C., then annealed at 350° C.,and then the surface thereof is nitrided by an Ar/N₂ plasma at 200° C.

FIG. 31 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 400° C. and no annealing is carriedout.

FIG. 32 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 400° C. and then the surface thereofis nitrided by an Ar/N₂ plasma at 400° C. without annealing.

FIGS. 33 (a) and (b) are diagrams showing an NiF₂ film forming methodand a Ni film forming method for comparison, respectively.

FIGS. 34 (a) and (b) are graphs showing the compositions of a Ni filmand an NiF₂ film, respectively.

FIGS. 35 (a) and (b) are diagrams showing the states before and afterannealing in the case where a Ni film of 50 nm is formed as a barriermetal layer and a Cu film is formed thereon.

FIGS. 36 (a) and (b) are diagrams showing diffusion of Cu, Ni, and so onbefore and after annealing when an NiF₂ film of 50 nm is formed as abarrier (metal) layer.

FIG. 37 is a diagram showing the results of elemental analysis in thedepth direction after the formation of the NiF₂ film.

FIG. 38 represents sectional SEM photographs showing a metallographicstructure in which a Cu layer is formed on an NiF₂ layer, wherein theright photograph enlarges a portion of the left photograph.

FIGS. 39 (a) and (b) are graphs showing the results of mutual diffusionevaluation of a sample having an NiF₂ film of 10 nm formed as a barrierlayer, wherein (a) is a diagram showing the state before a mutualdiffusion test (before annealing at 350° C.) and (b) is a diagramshowing the state after the mutual diffusion test (after annealing at350° C.).

DESCRIPTION OF SYMBOLS

-   -   1 barrier cap layer    -   2 first interlayer insulating film    -   2 a CFx film    -   2 b CFx film    -   3 first adhesive layer    -   4 second interlayer insulating film    -   5 second adhesive layer    -   6 hard mask    -   7 via hole    -   8 electrode    -   9 trench    -   10 interconnection structure    -   11 interconnection conductor (Cu)    -   12 antenna    -   13 gas introducing pipe    -   14 silicon wafer    -   21 insulator plate    -   22 lower shower plate    -   23 upper shower plate    -   24 process chamber    -   26 introducing pipe    -   30 outgas measuring apparatus    -   31 process chamber    -   32 discharge electrode    -   33 pipe    -   34, 35 pipe    -   36 a, 36 b pipe    -   37 a, 37 b vacuum pump    -   38 exhaust pipe    -   39 arrow    -   40 heating furnace    -   41 heating heater    -   42 photoion detector    -   44 mass flow controller    -   45 arrow    -   46 sample    -   47 introducing pipe    -   48 pipe    -   51 valve    -   52 exhaust pipe    -   53 valve    -   54 valve    -   56 pipe    -   57 mass flow controller    -   58 mass flow controller    -   59 arrow    -   61 variable displacement control valve    -   62 a, 62 b mass flow meter    -   63 arrow    -   64 arrow    -   65 pipe    -   66 arrow    -   71 barrier cap layer    -   72 SiOC film    -   73 PAR (low-permittivity Si layer)    -   74 hard mask    -   100 interconnection structure    -   102 plasma processing apparatus    -   103 outgas measuring system

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to facilitate understanding of this invention, a conventionalinterlayer insulating film structure of a semiconductor device accordingto prior art will be described with reference to FIG. 1 beforedescribing an embodiment of this invention.

Referring to FIG. 1, in the semiconductor device according to prior art,an interlayer insulating film structure (only one connecting portionbetween interconnection layers is shown) 100 provided on a semiconductorsubstrate (not shown) formed with a number of semiconductor elementscomprises a barrier cap layer 71 of silicon carbide (SiC) or the like, acarbon-containing silicon oxide (SiOC) film 72 formed on the barrier caplayer 71, a via hole 7 provided in the SiOC film 72, a trench 9 providedin a PAR (low-permittivity silicon (Si) layer 73), and a hard mask 74 ofsilicon oxide (SiO₂) covering them. A metal such as Cu is buried in thevia hole 7 to form an electrode or interconnection 8 and, at its upperend, Cu or the like is buried in the trench 9 to form an interconnection11.

Now, the embodiment of this invention will be described with referenceto the drawings.

As shown in FIG. 2, in a semiconductor device according to theembodiment of this invention, a multilayer interconnection structure(only one connecting portion between interconnection layers is shown) 10provided on a semiconductor substrate (not shown) formed with a numberof semiconductor elements has a first interlayer insulating film 2 inthe form of a fluorocarbon film (hereinafter referred to as a CFx film)formed on a barrier cap layer 1 of silicon carbonitride (SiCN).

A via hole 7 is provided so as to penetrate the first interlayerinsulating film 2 and the barrier cap layer 1. An electrode orinterconnection 8 of Cu is formed in the via hole 7. Further, a secondinterlayer insulating film 4 in the form of a fluorocarbon film isformed on the first interlayer insulating film 2 through a firstadhesive layer 3 of SiCN. Further, a hard mask 6 of silicon oxide (SiO₂)is provided on the second interlayer insulating film 4 through a secondadhesive layer 5 of SiCN.

Further, a trench 9 is provided from the hard mask 6 to the interlayerinsulating film 2 and an interconnection conductor 11 of Cu is buried inthis trench.

Herein, the barrier cap layer 1 and the first and second adhesive layers3 and 5 each have a permittivity of about 4.0, but hydrocarbon with ksmaller than 2.5 may be used as the barrier cap layer 1 and a thinnerSiCO film with k=3.0 may be used as each adhesive layer.

The interlayer insulating films 2 and 4 are each in the form of thefluorocarbon (CFx) film with k=2.0 and it is possible to further form afluorocarbon film with k=about 1.7.

Although the SiO₂ film with k=4.0 is used as the hard mask layer 6, itis possible to use an SiCO film with k smaller than 3.0.

Referring to FIG. 3, a thin CFx film 2 a is formed by CVD on theunderlayer 1 in the form of the SiCN layer by decomposition of a C₅F₈gas using a Xe plasma and a thick CFx film 2 b is formed by CVD on theCFx film 2 a by decomposition of a C₅F₈ gas using an argon (Ar) plasma.

Further, after forming or annealing the CFx film 2 b, the surface of theCFx film 2 b is nitrided by nitrogen radicals produced by introducing anN₂ gas into an Ar gas plasma, thereby reducing outgassing from the CFxfilms. With this configuration, the film stripping is prevented and thepermittivity can be controlled in a range of 1.7 to 2.2.

Referring to FIG. 4, a microwave is radiated from a radial line slotantenna (RLSA) 12 disposed through an insulator plate 21 in the upperpart of a plasma processing apparatus 102 and then is transmittedthrough the underlying insulator plate and a shower plate 23 into aplasma generating region. A Xe gas or an Ar gas is uniformly ejectedinto the plasma generating region from the upper shower plate 23 througha gas introducing pipe 13, so that a plasma is excited by the microwaveradiated into the plasma generating region.

A lower shower plate 22 is disposed in a diffusion plasma region of themicrowave-excited plasma processing apparatus.

Herein, if a Xe, Kr, or Ar gas is caused to flow into the upper showerplate 23 through the introducing pipe 13 and an SiH₄ gas is caused toflow into the lower shower plate 22 through an introducing pipe 26, asilicon (SiO₂) film can be formed on the surface of a substrate, forexample, a silicon wafer, 14.

On the other hand, if a Kr, Xe, or Ar gas is caused to flow from theupper shower plate 23 and a CxFy (C₅F₈, C₄F₈, or the like) gas is causedto flow from the lower shower plate 22, a fluorocarbon film can beformed.

It is necessary that an oxygen gas or an N₂/H₂ or NH₃ gas be caused toflow from the upper shower plate 23 for oxidation or nitridingtreatment, while, a mixed gas of an oxidizing gas and a nitriding gas,such as an O₂/NH₃, O₂/N₂O, or O₂/NO gas, be caused to flow therefrom inthe case of oxynitriding treatment.

The substrate (e.g. silicon wafer) 14, i.e. the object to be processed,is placed in a process chamber 24 at a place where a plasma is diffusedand directly irradiated, and is oxidized by oxygen radicals or the likeexcited by the plasma. In this event, it is desirable that the object tobe processed be placed not in a space where the plasma is excited, butin a space where the plasma is diffused, in the process chamber 24.

Exhaust gases in the process chamber 31 pass through an exhaust duct vianon-illustrated exhaust ports and then are introduced into a small pumpfrom its inlet ports.

As shown in FIG. 5, the electron temperature becomes substantiallyconstant when the distance between a shower plate and an electrodebecomes 30 mm or more, and the electron temperature is lowered in theorder of Ar, Kr, and Xe.

In any of the foregoing cases, since a Kr or Xe gas has, as comparedwith Ar, a smaller sectional area for collision with electrons and asmaller ionization energy where the electron temperature is low, when amicrowave is irradiated to the Xe (or Kr) gas, the electron temperatureof a plasma is lowered and thus it is possible to suppress damage tovarious formed films in the film formation and to suppress the etchingaction of a C₅F₈ gas.

Referring to FIG. 6, an outgas measuring system 103 comprises an outgasmeasuring apparatus 30 and a photoion measuring apparatus.

A sample 46 is placed in a heating furnace 40 of the photoion measuringapparatus. As indicated by an arrow 45, Ar is introduced as a carriergas into the heating furnace 40 through an introducing pipe 47 whilebeing adjusted to a flow rate of 100 sccm by a mass flow controller 44.

The heating furnace 40 is provided with heating heaters 41 and aphotoion detector 42. Gases released from the sample 46 are introducedinto the outgas measuring apparatus 30 through a pipe 48 provided with avalve 53. An exhaust pipe 52 provided with a valve 51 for exhaust isbranched from the pipe 48.

The outgas measuring apparatus 30 is provided with a discharge electrode32. Through pipes 36 a and 36 b provided with vacuum pumps 37 a and 37b, respectively, and an exhaust pipe 38 where the pipes 36 a and 36 bjoin together, the gases inside the outgas measuring apparatus 30 areexhausted as indicated by an arrow 39. On the other hand, pipes 34 and35 are respectively provided on the inside of the outgas measuringapparatus 30 and at its adjacent portion where the discharge electrode32 is provided. The pipe 34 is exhausted at a flow rate of 600 sccmthrough a variable displacement control valve 61 and a mass flow meter62 a as indicated by an arrow 63. On the other hand, the pipe 35 isexhausted at a flow rate of 550 sccm through a mass flow meter 62 b asindicated by an arrow 64. The two pipes 34 and 35 join together to be apipe 65 and are exhausted as indicated by an arrow 66.

A pipe 33 provided with a mass flow controller 58 for introducing an Argas at 1 SLM as indicated by an arrow 59 is connected to the outgasmeasuring apparatus 30 at a position which is the same in the lengthdirection as that of the pipe 34, but differs therefrom in thecircumferential direction. The pipe 48 is provided with the valve 53 ona further downstream side as compared with the exhaust pipe 52 and apipe 56 provided with a mass flow controller 57 for introducing an Argas for dilution at 500 sccm is connected to the pipe 48 through a valve54 on a further downstream side. The pipe 48 is connected to the outgasmeasuring apparatus 30 at a position which is the same in the lengthdirection as that of the exhaust pipe 35, but differs therefrom in thecircumferential direction.

Next, the CFx film forming process according to the embodiment of thisinvention will be described in detail.

Referring to FIG. 3, in the CFx film forming process according to theembodiment of this invention, SiCN or SiCO is first formed as anunderlayer by plasma treatment using SiH₄/C₂H₄/N₂ or O₂, or the like bythe use of the apparatus shown in FIG. 4. Naturally, organic silane maybe used instead of silane gas (SiH₄)/ethylene (C₂H₄).

Then, a thin first CFx film 2 a of 5 to 10 nm is formed on theunderlayer 1 by a Xe plasma using a fluorocarbon gas as a reactive gas.

Herein, as the fluorocarbon gas as the reactive gas, use can be made ofunsaturated aliphatic fluoride expressed by a general formulaO_(n)F_(2n) (where n is an integer of 2 to 8) or O_(n)F_(2n-2) (n is aninteger of 2 to 8), but is preferably made of fluorocarbon expressed bya general formula C₅H₈, such as carbon fluoride containingoctafluoropentyne, octafluoropentadiene, octafluorocyclopentene,octafluoromethylbutadiene, octafluoromethylbutyne, fluorocyclopropene,or fluorocyclopropane, or carbon fluoride containing fluorocyclobuteneor fluorocyclobutane.

Further, switching the Xe gas to an Ar gas, a second CFx film 2 b havinga thickness of 380 to 500 nm is formed on the first CFx film 2 a by anAr plasma using a C₅F₈ gas as a reactive gas. Since the permittivity ofa CFx film is reduced when formed using a plasma of Ar gas, this makesit possible to reduce the permittivity of the CFx film 2 to as low as1.7 to 2.2.

After forming the fluorocarbon films on the substrate, it is possible tocarry out cleaning of the inner wall of the chamber by generating aplasma using a mixed gas of hydrogen and oxygen in the chamber.

Further, after the film formation or annealing, the surface of the CFxfilm is nitrided by an Ar/N₂ plasma or an N₂ plasma. This makes itpossible to reduce outgassing from the CFx films.

Preferably, annealing is performed after the film formation and beforethe surface nitriding. In this specification, the annealing may beperformed in the plasma chamber with the substrate as it is withoutexposing the substrate to the atmosphere or may be performed using aseparate annealing apparatus. In either case, an atmosphere is set to aninert gas atmosphere and the pressure may be set to an atmosphericpressure but is preferably set to a reduced pressure of about 1 Torr. Aswill be described later, it is preferable that the fluorocarbon film beirradiated with an Ar plasma before or after the annealing.

A description will be given of a method of manufacturing theinterconnection structure of FIG. 2. As shown in FIG. 2, a firstinterlayer insulating film 2 shown in FIG. 3 is formed using a barriercap layer 1 as an underlayer. A via hole 7 is formed in the firstinterlayer insulating film 2 by etching. Then, as a barrier layer forpreventing diffusion of an electrode metal into the interlayerinsulating film, a film of a fluoride of nickel, preferably a nickeldifluoride (referred to as NiF₂) film is formed on the inner wall of thevia hole 7 by forming a film of nickel by PVD and then fluorinating it,or is directly formed thereon by MOCVD.

Then, likewise, an SiCN layer or a carbon-containing silicon oxide(SiCO) layer is formed as an underlayer 3 in the form of an adhesivelayer and, thereon, an interlayer insulating film 4 comprising a firstand a second CFx film is formed in the same manner as shown in FIG. 3.On this interlayer insulating layer 4, an SiCN layer or an SiCO layer isfurther formed as an underlayer 3 for adhesion and, on this underlayer3, an SiO₂ or SiCO layer is formed as a hard mask layer 6.

Herein, the SiO₂ layer can be formed by introducing a mixed gas of Arand O₂ from the upper shower plate 23 and introducing an SiH₄ gas fromthe lower shower plate 22 in the plasma processing apparatus 102 shownin FIG. 4. The SiCO layer is the same as described before.

Then, a trench 9 is formed by etching, a non-illustrated NiF₂ barrierlayer is formed on the inner wall surface of the trench 9, and Cu isfilled as a metal in the trench 9 to form an interconnection conductor11, so that the interconnection structure 10 is completed.

Herein, a description will be given of release of SiFx gases when anunderlayer 1 is made of a silicon compound and a CFx film is formedthereon.

SiFx gases are produced by reactions at the interface between a layer ofSi, SiO₂, Si₃N₄, or the like and a CFx film.

Table 1 below shows the ionization potentials of outgases. As shown inTable 1, it is seen that the ionization potential of SiFx increases inthe order of SiF, SiF₃, SiF₂, and SiF₄.

TABLE 1 Element m/z Ionization Potential (eV) Ar 40 15.8 SiF₄ 104 15.7H₂ 2 15.4 N₂ 28 15.6 O₂ 32 12.1 H₂O 18 12.6 SiF₂ 66 10.78 SiF₃ 85 9.3SiF 47 7.298

The release of SiFx gases depends on an underlayer in the initial filmformation.

FIG. 7 represents diagrams showing the temperature dependence of SiFxoutgassing per different underlayer, wherein the left scale shows theoutgas amount when the temperature represented by the right scale isapplied, with the lapse of time, to (a) a CFx film formed on a Siunderlayer (CFx/Si), (b) a CFx film formed on an SiO₂ underlayer(CFx/SiO₂), and (c) a CFx film formed on an Si₃N₄ underlayer(CFx/Si₃N₄). As shown in FIGS. 7( a), (b), and (c), it is seen that theSiFx outgassing changes by changing the underlayer. It has been foundthat the reactions at the CFx/underlayer interface are such that theoutgassing decreases in amount in the order of Si, SiO₂, and Si₃N₄.

FIG. 8 is a diagram showing the temperature dependence of SiF-basedoutgas amounts. As shown in FIG. 8, it is seen that reactions occur atthe interface between SiO₂ and CFx to produce SiFx outgases. Therefore,it is understood that it is essential to suppress the interfacialreactions. A further detailed investigation was made of SiF₄.

FIG. 9 is a diagram showing time-dependent changes of SiF₄ spectra.Referring to FIG. 9, it is seen that, in the outgas measurement using astandard CFx film, when the temperature is raised with CFx/SiO₂, SiF₄ isproduced and continues to be produced for 16 hours. Therefore, it isseen that it is essential to suppress the reactions at the CFx film/SiO₂interface.

Next, an investigation was made of the temperature dependence ofSiF-based outgas amounts for a CFx film formed on such an underlayer.

FIG. 10 represents diagrams showing the temperature dependence ofSiF-based outgas amounts, wherein (a) shows the temperature dependenceof outgas amounts in the case of film formation using Ar and (b) showsit in the case of film formation using Xe. The conditions were pressure4 Pa (30 mTorr), 900 W, and X-ray diffractometer (SSY-1)/Ar (Xe)=10/240(210) sccm.

From FIG. 10( a) and FIG. 10( b), it has been found that the SiF-basedoutgassing can be reduced by performing the film formation using aXe-diluted gas as compared with the case where the film formation isperformed using Ar as a dilution gas. That is, it has been found thatthe low electron temperature is essential for reducing the outgassing.

Next, the temperature dependence of SiFx outgas amounts was investigatedby using Xe in the initial film formation on a Si underlayer and thenswitching it to Ar.

FIG. 11 is a diagram showing the temperature dependence of SiFx gasamounts when an underlayer is made of Si. The conditions were such that,using C₅F₈ as a reactive gas, film formation was performed by plasmatreatment using Xe at 26.6 Pa (200 mTorr) for 5 seconds, then filmformation was performed by plasma treatment using Ar at 26.6 Pa (200mTorr) and, after annealing, treatment was performed using Ar at 26.6 Pa(200 mTorr) for 5 seconds. As shown in FIG. 11, it has been found thatthe SiFx gases can be reduced by using Xe in the initial film formation.

FIG. 12 represents diagrams showing the temperature dependence ofSiFx-based outgas amounts, wherein (a) shows the outgas amounts from aCFx film obtained by treatment with C₅F₈/Xe at 26.6 Pa (200 mTorr) for 5seconds, then treatment with C₅F₈/Ar at 26.6 Pa (200 mTorr) and, afterannealing, treatment with Ar at 26.6 Pa (200 mTorr) for 5 seconds and(b) shows the outgas amounts from a CFx film obtained by treatment (5seconds) in which a Xe plasma is on and C₅F₈ is introduced, then, afterthe introduction of C₅F₈ is off and the Xe plasma is off, Ar/C₅F₈treatment for 3 minutes and then Ar+N₂ treatment for 5 seconds.

From FIG. 12( a) and FIG. 12( b), it is seen that the SiFx gases arereduced by using Xe in the initial film formation and carrying out theinterface control.

Next, the temperature dependence of SiF4 outgas amounts was investigatedby similarly forming a CFx film on a Si underlayer while changing theconditions.

FIG. 13 shows the temperature dependence of SiFx outgas amounts when anunderlayer is made of Si. In the process, treatment was performed for 5seconds while a Xe plasma was on and a C₅F₈ gas was introduced, then theC₅F₈ gas was off and the Xe plasma was off, then Ar/C₅F₈ treatment wasperformed for 3 minutes, and subsequently, Ar+N₂ surface nitridingtreatment was performed for 5 seconds. From FIG. 13, it is seen that theSiFx outgas amounts can be reduced by changing the sequence.

Further, an investigation was made of the TDS outgas spectra of a CFxfilm formed by an Ar plasma.

FIG. 14 is a diagram showing the TDS outgas spectra of a CFx film of 120nm formed on a Si underlayer. As shown in FIG. 14, it is seen that whenthe temperature is raised at a heating rate of 60° C./min from roomtemperature to 400° C., CF-based outgases and so on are produced.

FIG. 15 is a diagram showing the temperature dependence of CFx outgasamount, after annealing, of a CF film formed on an SiO₂ underlayer. Asshown in FIG. 15, it has been found that, by removing insufficientlybonded components through annealing, subsequent decomposition reactionsdo not occur, thus confirming that the annealing is necessary.

FIG. 16 is a diagram showing the temperature dependence of releasedwater amount, after CF-film annealing, of a CF film formed on an SiO₂underlayer in the same manner. As shown in FIG. 16, it has been foundthat, once heated, there is no generation of water in an in-situprocess, and thus it is seen that the in-situ process is essential.

FIG. 17 is a diagram showing the fluorocarbon outgas characteristicsafter Ar/N₂ plasma treatment using the apparatus of FIG. 5 and theresults of thermal desorption spectrometry (TDS) measurement. Theheating rate is 0.17° C./sec. The sample shown in FIG. 5 shows theoutgas characteristics of a CFx film formed at 220° C. usingstraight-chain C₅F₈ as a reactive gas shown in FIG. 4 and then in-situannealed at 330° C.

As shown in FIG. 17, the heating was stopped after 40 seconds from thestart of the heating, so that the temperature was maintained at aconstant value of 400° C. It is seen that the release extremelyincreases near 350° C. and becomes maximum at a temperature somewhatlower than 400° C.

Next, the temperature dependence of outgas amount of a CFx film wasinvestigated by introducing C₅F₈ in Ar-plasma treatment.

FIG. 18 represents diagrams showing the temperature dependence ofCFx-based outgas amount in the case where C₅F₈ is introduced inAr-plasma treatment, then the introduction is stopped in the plasmatreatment, and then the Ar-plasma treatment is stopped, wherein (a)shows the relationship between the relative intensity of CFx outgas andthe time and (b) shows the relationship between the H₂O concentration(ppb/cm²) for released water and the time. As shown in FIG. 18( a) andFIG. 18( b), it is seen that dangling components are reduced by causingthe material gas to flow in the plasma treatment. Further, it is seenthat the released water is also reduced and thus the effective surfacearea is reduced.

The outgas characteristics of this CFx film were investigated byannealing it after the formation thereof.

FIG. 19 represents diagrams showing the annealing temperature dependenceof outgas amounts of the CFx film, wherein (a) shows the outgas amountof a CF-based gas and (b) shows the outgas amount of an H₂O gas. FromFIGS. 19( a) and (b), it is seen that, by removing insufficiently bondedcomponents through annealing at 400° C., subsequent decompositionreaction processes do not occur. Further, it is seen that, once heated,there is no generation of water in an in-situ process, and thus it isseen that the in-situ process is essential for the annealing.

FIG. 20 represents diagrams showing the spectral of various outgasesaccording to a difference in leaving time of a CFx film, wherein (a)shows the results of measurement after being left standing in theatmosphere for 12 hours after annealing at 400° C. and (b) shows theresults of measurement after being left standing in the atmosphere for48 hours without annealing. From a comparison between FIGS. 20 (a) and(b), an HF outgas increases due to being left standing in theatmosphere. This represents that water in the atmosphere and the CFxfilm reacted with each other.

FIG. 21 represents diagrams showing the temperature dependence ofSi-based outgas amount, wherein (a) shows the temperature dependence ofCFx outgassing and (b) shows the temperature dependence of waterrelease. Referring to FIG. 21( a) and FIG. 21( b), an Ar plasma wasirradiated for 5 seconds after the treatment, and then annealing wascarried out. By the Ar plasma irradiation before the annealing, the CFxoutgassing is reduced to ⅔ so that insufficiently bonded CFx is reduced.Further, as shown in FIG. 21( b), the water release is also reduced to ½and thus the effective surface area is reduced.

Further, after annealing a CFx film at 400° C., an Ar/N₂ plasma wasirradiated for 5 seconds to nitride the surface.

FIG. 22 represents diagrams showing the surface nitriding effects,wherein (a) and (b) show the CFx outgassing effect and the water releaseeffect, respectively, when the Ar/N₂ plasma was irradiated for 5 secondsafter the annealing. Referring to FIG. 22( a) and FIG. 22( b), it isseen that the CFx gas is reduced to ⅓ as compared with the standardcondition by the Ar/N₂ plasma irradiation after the annealing. Further,it is seen that the released water is also reduced to ⅓ and thus theeffective surface area is reduced.

FIG. 23 shows the results of measurement of a sample formed with a CFxfilm and subjected to Ar/N₂ plasma irradiation after annealing like inFIG. 17, using an X-ray photoelectron spectrometer (ESCA: ElectronSpectroscopy for Chemical Analysis). From the results of FIG. 23, it hasbeen found that N atoms were detected only in several nm from thesurface and thus the outgassing was reduced by the surface qualityimprovement by the annealing. The permittivity of the CFx film was 2.04before the outgassing while it was 2.08 after the outgassing, and thusno large change was observed.

FIG. 24 represents diagrams showing the film forming conditiondependence of outgas amounts of a CFx film, wherein (a) shows CF-basedoutgassing and (b) shows H₂O-based outgassing. As shown in FIG. 24, itis seen that the CFx outgassing is reduced by Ar/N plasma irradiationfor 5 seconds after annealing at 400° C. to thereby Ar/N₂-treat thesurface (surface nitriding). It is seen that the CFx outgassing isreduced to ⅓ as compared with no annealing.

FIG. 25 represents diagrams showing the results of outgassing in thecase of Ar/N₂ plasma treatment after annealing a CFx film formed to 400nm, wherein (a) shows the results with no nitriding being the normalcondition and (b) shows the results with nitriding. It is seen that theoutgassing is small in amount by the Ar/N₂ nitriding treatment.

FIG. 26 is a diagram showing the outgas TDS spectra of an SiCN filmin-situ formed on a CFx film (SiCN/CFx) formed on a Si underlayer. Asshown in FIG. 26, it is seen that outgassing is reduced by forming theSiCN film as a cap layer on the CFx film.

Next, the surface quality improvement achieved by annealing andsubsequent nitriding treatment will be described using FIGS. 27 to 31.

FIG. 27 shows the temperature dependence of CF-based outgas amount whena CFx film is formed on SiO₂ at 200° C. and annealed in Ar at 350° C.for 30 minutes. Referring to FIG. 27, it is observed that, by removinginsufficiently bonded components through annealing, decompositionreactions do not occur even if the temperature is raised to 400° C.thereafter, and the outgas amount of CF-based gas is reduced.

FIG. 28 is a diagram showing the temperature dependence of outgas amountin the case where nitriding treatment is performed by an Ar/N₂ plasma at200° C. after film formation at 200° C. and annealing at 350° C. Asshown in FIG. 28, it has been found that when a CFx film is formed onSiO₂, then annealed at 350° C., and then irradiated with an Ar/N₂ plasmaat 200° C., the outgassing is extremely reduced and thus the filmsurface quality improvement effect is large.

FIG. 29 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 350° C. and no annealing is carriedout.

FIG. 30 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 350° C., then annealed at 350° C.,and then the surface thereof is nitrided by an Ar/N₂ plasma at 200° C.As a result of comparing FIG. 30 with FIG. 29, it has been found thatthe outgassing is suppressed and the surface quality is improved byannealing and then nitriding the surface.

FIG. 31 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 400° C. and no annealing is carriedout. As shown in FIG. 31, the outgassing is observed after forming theCFx film on Si at 400° C. and then annealing it at 350° C.

FIG. 32 is a diagram showing the outgas amount in the case where a CFxfilm is formed on a Si substrate at 400° C. and then irradiated with anAr/N₂ plasma without annealing. As shown in FIG. 32, it is seen that theoutgassing increases when the nitriding treatment is performed by theAr/N₂ plasma at 400° C.

Therefore, from the results of FIGS. 27 to 32, it is seen that theeffect of the annealing is large and, by the surface nitriding with theAr/N₂ plasma at about 200° C., the outgassing decreases and the surfaceis improved in quality. Further, it has been confirmed that the adhesionincreases. Further, it has been found from the results of otherexperiments that the adhesion increases in the case of nitriding at ahigh temperature exceeding 200° C. (preferably 300° C. to 400° C.) andthat, in the case of plasma treatment using only N₂ with no Ar gas, theadhesion is improved, the surface roughness is small, and the outgasamount is reduced.

Next, referring to FIGS. 33 to 39, a description will be given of thestructure and effect of using an NiF₂ film as a barrier layer.

FIGS. 33( a) and (b) are diagrams showing an NiF₂ film forming methodand a Ni film forming method for comparison, respectively. FIGS. 34( a)and (b) are graphs showing the compositions of a Ni film and an NiF₂film, respectively. FIGS. 34( a) and (b) show that a Ni film (afterannealing at 350° C.) and an NiF₂ film are formed on SiO₂, respectively.

FIGS. 35( a) and (b) show the states before and after annealing in thecase where a Ni film of 50 nm is formed as a barrier metal layer and aCu film is formed thereon, wherein it is shown that Ni diffuses into theCu film and Cu diffuses into the Ni film.

FIGS. 36( a) and (b) show that when an NiF₂ film of 50 nm is formed as abarrier (metal) layer, no diffusion of Cu or Ni occurs before and afterannealing and thus, when the NiF₂ film is used as the barrier layer, itcompletely functions as a barrier to Cu.

FIG. 37 is a diagram showing the results of elemental analysis in thedepth direction after the formation of the NiF₂ film. FIG. 38 representssectional SEM photographs showing a metallographic structure in which aCu layer is formed on an NiF₂ layer, wherein the right photographenlarges a portion of the left photograph.

FIG. 39( a) and FIG. 39( b) are graphs showing the results of mutualdiffusion evaluation of a sample having an NiF₂ film of 10 nm formed asa barrier layer, wherein (a) is a diagram showing the state before amutual diffusion test (before annealing at 350° C.) and (b) is a diagramshowing the state after the mutual diffusion test (after annealing at350° C.). FIGS. 39( a) and (b) show that there is no diffusion of Cu orNi even after the annealing and thus it completely functions as abarrier to Cu.

INDUSTRIAL APPLICABILITY

As described above, an interlayer insulating film comprising a CFx filmaccording to this invention and its manufacturing method and aninterconnection structure and its manufacturing method are optimum for asemiconductor device or a wiring board having a low-permittivityinterlayer insulating film and an interconnection structure, or anelectronic device including them.

1. An electronic device having a multilayer interconnection structure,said electronic device comprising, as an interlayer insulating film ofsaid multilayer interconnection structure, at least a fluorocarbon filmnitrided at its surface formed on an underlayer.
 2. The electronicdevice according to claim 1, wherein said underlayer includes at leastone of an SiCN layer, an Si₃N₄ layer, an SiCO layer, and an SiO₂ layer.3. The electronic device according to claim 1, further comprising atleast one of an Si₃N₄ layer, an SiCN layer, and an SiCO layer formed onsaid fluorocarbon film.
 4. The electronic device according to claim 1,wherein said fluorocarbon film is formed by CVD using a plasma generatedby using a rare gas.
 5. The electronic device according to claim 1,wherein a thickness of a nitrided portion of said surface is 1 to 5 nm.6. The electronic device according to claim 1, wherein a thickness of anitrided portion of said surface is 2 to 3 nm.
 7. An electronic devicehaving a multilayer interconnection structure, said electronic devicecomprising an interlayer insulating film of said multilayerinterconnection structure having a fluorocarbon film nitrided at itssurface, a contact hole, a metal containing at least copper filled insaid contact hole, and a barrier layer interposed between saidfluorocarbon films and said metal at a side surface of said contacthole.
 8. The electronic device according to claim 7, wherein saidbarrier layer includes at least a layer of a fluoride of nickel.
 9. Amethod of manufacturing an electronic device having a multilayerinterconnection structure, the method including a step of forming afluorocarbon film on an underlayer using a fluorocarbon gas and a raregas, and a step of nitriding a surface of said fluorocarbon film. 10.The method according to claim 9, wherein said underlayer includes atleast one of an SiCN layer, an Si₃N₄ layer, an SiO₂ layer, and an SiCOlayer.
 11. The method according to claim 9, further comprising, afterthe step of forming said fluorocarbon film, a step of generating aplasma using a mixed gas of hydrogen and oxygen in a chamber, therebycleaning an inner wall of said chamber.
 12. A method of manufacturing anelectronic device having a multilayer interconnection structure, saidmethod comprising a step of forming a fluorocarbon film as at least aportion of an interlayer insulating film, and a step of nitriding asurface of said fluorocarbon film.
 13. The method according to claim 12,wherein said step of nitriding is performed in a plasma containing an N₂gas.
 14. The method according to claim 12, further comprising, a step ofirradiating the surface of said fluorocarbon film with a rare gasplasma.
 15. The method according to claim 12, further comprising a stepof forming a contact hole in said fluorocarbon film and a step offilling a metal in said contact hole.
 16. The method according to claim12, further comprising a step of forming a contact hole in saidfluorocarbon film, a step of filling a conductive material containing atleast copper in said contact hole and a step of forming a barrier layeron a side surface of said contact hole for preventing diffusion of saidcopper.